Clear recently opened files from the Start menu in Windows 7

Click on the Start button, right-click on Recent Items and click on Clear recent items list to clear recently opened files from the Start menu.
If you open files after performing the above then the recently opened files will appear under Recent Items. To clear this list permanently, perform the following:

1. Right-click on an empty space on the taskbar and click on Properties.
2. From the Taskbar and Start Menu Properties dialog box, click on the Start Menu tab. Under Privacy section, click to remove the check mark beside Store and display recently opened items in the Start menu and the taskbar.
3. Click Apply and then click OK.